1. Field of the Invention
This invention relates to a light beam scanning apparatus using an ultrasonic light deflector.
2. Description of the Prior Art
Light beam scanning apparatuses for scanning light having a predetermined wavelength, for example a laser beam, have heretofore been used for writing and reading image information. In the light beam scanning apparatuses, a multi-face rotating mirror, a bimorph mirror, a hologram scanner, and the like are used. However, the light beam scanning apparatuses have the drawback that, since a light reflecting plane or a plane of diffraction is mechanically rotated or swung, the moveable sections are inevitably worn out and it is not always possible to improve durability of the moveable sections. Also, since worn moving sections, particularly worn bearings, cause the reflecting plane or the place of diffraction to deviate, the quality of the written image or the read-out image becomes very low.
Therefore, a need exists for a light deflecting device having no moveable section, and an ultrasonic light deflector, i.e. an acousto-optic deflector (AOD), has been proposed as such light deflecting device. However, the ultrasonic light deflector has the drawback that the light deflection angle is small and the number of the resolution points on one scanning line cannot be increased sufficiently. For this reason, application of the ultrasonic light deflector is strictly limited.